Restore KeyedServiceFactory diagnostics for context use-after-destroy.

chrome/browser/engagement/site_engagement_service.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/engagement/site_engagement_service.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 104 matching lines @@
                      content::BrowserThread::UI),
       base::Bind(&SiteEngagementService::AfterStartupTask,
                  weak_factory_.GetWeakPtr()));
 
   if (!g_updated_from_variations) {
     SiteEngagementScore::UpdateFromVariations(kEngagementParams);
     g_updated_from_variations = true;
   }
 }
 
-SiteEngagementService::~SiteEngagementService() {
+SiteEngagementService::~SiteEngagementService() = default;
+
+void SiteEngagementService::Shutdown() {
   history::HistoryService* history = HistoryServiceFactory::GetForProfile(
       profile_, ServiceAccessType::IMPLICIT_ACCESS);
   if (history)
     history->RemoveObserver(this);
 }
 
 blink::mojom::EngagementLevel
 SiteEngagementService::GetEngagementLevel(const GURL& url) const {
   if (IsLastEngagementStale())
     CleanupEngagementScores(true);
@@ skipping 512 matching lines @@
     if (!engagement_score.last_shortcut_launch_time().is_null() &&
         engagement_score.last_shortcut_launch_time() > last_visit) {
       engagement_score.set_last_shortcut_launch_time(last_visit);
     }
 
     engagement_score.Commit();
   }
 
   SetLastEngagementTime(now);
 }